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61.
Positive muons have been used to monitor the proton and deuteron mobilities in mixed, concentrated NbH_xD_y hydrides, with
x+y= constant. The mobility of the muons decreases linearly with increasing D‐content, which is expected if the protons and
the deuterons move in an uncorrelated fashion. Combined with other evidence which suggests that such correlations exist, the
present observation may be interpreted as due to a destruction of a correlated motion of H’s or D’s in the vicinity of the
muons.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
62.
Analysis of mucosal mucins separated by SDS-urea agarose polyacrylamide composite gel electrophoresis 总被引:1,自引:0,他引:1
Efficient separation of mucins (200 kDa-2 MDa) was demonstrated using gradient SDS agarose/polyacrylamide composite gel electrophoresis (SDS-AgPAGE). Inclusion of urea (SDS-UAgPAGE) in the gels casting were shown to have no effect on the migration of mucins in the gel and allowed casting of gel at room temperature. This simplified the procedure for multiple casting of agarose polyacrylamide gradients and increased reproducibility of these gels. Hence, the implementation of urea makes the technique applicable for high throughput isolation and screening of mucin oligosaccharides by LC-MS after releasing the oligosaccharides from isolated, blotted mucin subpopulations. It was also shown that the urea addition had no effect on other supporting applications such as western and lectin blotting. In addition, identification of the mucin protein after tryptic digestion and LC-MS was possible and no protein carbamylation due to the presence of urea in the gel was detected. LC-MS software developed for metabolomic analysis was used for O-linked oligosaccharide detection and differential display of various mucin samples. Using this method, heterogeneous glycosylation of mucins and mucin-type molecules isolated by SDS-AgPAGE and SDS-UAgPAGE was shown to consist of more than 80 different components in a single band, and in the extreme cases, up to 300-500 components (MUC5B/AC from saliva and sputum and). Metabolomic software was also used to show that the migration of mucin isoforms within the gel is due to heterogeneous size distribution of the oligosaccharides, with the slower migrating bands enriched in high-molecular-weight oligosaccharides. 相似文献
63.
Verho O Johnston EV Karlsson E Bäckvall JE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(40):11216-11222
The synthesis of a new series of cyclopentadienylruthenium catalysts with varying electronic properties and their application in racemization of secondary alcohols are described. These racemizations involve two key steps: 1) β-hydride elimination (dehydrogenation) and 2) re-addition of the hydride to the intermediate ketone. The results obtained confirm our previous theory that the electronic properties of the substrate determine which of these two steps is rate determining. For an electron-deficient alcohol the rate-determining step is the β-hydride elimination (dehydrogenation), whereas for an electron-rich alcohol the re-addition of the hydride becomes the rate-determining step. By matching the electronic properties of the catalyst with the electronic properties of the alcohol, we have now shown that a dramatic increase in racemization rate can be obtained. For example, electron-deficient alcohol 15 racemized 30 times faster with electron-deficient catalyst 6 than with the unmodified standard catalyst 4. The application of these protocols will extend the scope of cyclopentadienylruthenium catalysts in racemization and dynamic kinetic resolution. 相似文献
64.
Wiklander J Karlsson BC Aastrup T Nicholls IA 《Analytical and bioanalytical chemistry》2011,400(5):1397-1404
A series of streptavidin-mimicking molecularly imprinted polymers has been developed and evaluated for their biotin binding characteristics. A combination of molecular dynamics and NMR spectroscopy was used to examine potential polymer systems, in particular with the functional monomers methacrylic acid and 2-acrylamidopyridine. The synthesis of copolymers of ethylene dimethacrylate and one or both of these functional monomers was performed. A combination of radioligand binding studies and surface area analyses demonstrated the presence of selectivity in polymers prepared using methacrylic acid as the functional monomer. This was predicted by the molecular dynamics studies showing the power of this methodology as a prognostic tool for predicting the behavior of molecularly imprinted polymers.
The biotin binding characteristics of a series of molecularly imprinted polymers have been evaluated and correlated to predictions made by molecular dynamics simulations and 1H-NMR titrations 相似文献
65.
66.
Ek M Borgstr?m MT Karlsson LS Hetherington CJ Wallenberg LR 《Microscopy and microanalysis》2011,17(5):752-758
The twin interface structure in twinning superlattice InP nanowires with zincblende structure has been investigated using electron exit wavefunction restoration from focal series images recorded on an aberration-corrected transmission electron microscope. By comparing the exit wavefunction phase with simulations from model structures, it was possible to determine the twin structure to be the ortho type with preserved In-P bonding order across the interface. The bending of the thin nanowires away from the intended 110 axis could be estimated locally from the calculated diffraction pattern, and this parameter was successfully taken into account in the simulations. 相似文献
67.
Martin Månsson Oscar Tjernberg Tomas Claesson Henrik S. Karlsson Ulf O. Karlsson 《Applied Surface Science》2006,252(15):5308-5311
Transiently excited electron states at the GaSb(0 0 1) surface have been studied by means of time- and angle-resolved photoemission spectroscopy based on a femtosecond laser system. A normally unpopulated surface electron state has been found at ∼250 meV above the valence band maximum with a strong confinement at the center of the surface Brillouin zone. The lifetime of transiently excited carriers at the intergap surface states has been found to be ∼11 ps, associated with rapid carrier diffusion. 相似文献
68.
In this work the three dipeptides, Z-l-alanyl-l-glutaric acid (Z-l-ala-l-glu), Z-l-phenylanyl-l-glutaric acid (Z-l-phe-l-glu) and Z-glycyl-l-glutaric acid (Z-gly-l-glu) were tested as chiral counter ions for enantiomeric resolution of amino alcohols. The influence of solute and counter
ion structure upon retention and enantioselectivity was evaluated. The chiral counter ions were dissolved in a mixture of
polar solvents, i.e., ethyl acetate, methanol and acetonitrile and the achiral solid phase used was porous graphitic carbon,
marketed as Hypercarb. The enantioselectivities observed for the tested solutes were highly influenced by the used chiral
counter ion structure. For example no enantioselectivity was observed for (R,S)-alprenolol using Z-l-ala-l-glu while a separation factor (α) of 1.59 was obtained using Z-l-phe-l-glu as chiral counter ion. High selectivity factors (α > 2.7) were observed between enantiomers of tertiary amines using Z-l-phe-l-glu as counter ion. Interestingly, the structure of the counter ion, as well as the charge on Z-l-phe-l-glu and the mobile phase solvent composition, influenced the retention order of the enantiomers. 相似文献
69.
Rolf G. Karlsson 《BIT Numerical Mathematics》1988,28(1):19-26
A fast solution to the complete minimum matching problem using a greedy heuristic is presented, when the points are distributed on a grid domain. For this a data structure which efficiently supports nearest neighbor searches and deletions from a planar point set is developed. 相似文献
70.
A miniaturized continuous gradient elution system was designed for work with packed capillary columns. The retention reproducibility achieved is adequate for many practical applications. 相似文献